president obama has arrived for the service. former presidents george w. bush, jimmy carter and bill clinton will all be attending. memorial service for mandel washington d-c. >>> also tonight we'll be introduced to a group of bay area kids who will play a special role in that memorial service for mandela in washington d.c. >> reporter: as beautifully as he sings for oakland pacific boy choir academy, 8th grader aaron sanchez speaks just as beautifully about the moment he found out nelson mandela died. >> a voice of the world has just gone away. we'll never hear it again. >> reporter: the former south african president's death four days ago hit especially hard at this school. >> we have a special connection with south africa. >> reporter: the grammy award winning boys choir has traved the world, but it was a trip to south africa in 2009 that 9th grader brendan singer said had the greatest impact. they traveled to nelson mandela's home. >> being in his house, seeing where he stood like where he got all his great ideas of. >> reporter: they learned to sing i